Glycerin is not good to use in extremely humid or dry weather. Glycerin draws the moisture to what is drier. Since I live in a desert, using products with lots of glycerin makes my hair dry and brittle because the glycerin takes away moisture from the hair and gives it to the drier air. Glycerin itself isn't bad; it depends on the climate and dew point.

Originally Posted by multicultcurly

This. I use to live in Kansas, which was so SO dry. I couldn't a lot of stuff to deal with the dry air - silicones, glycerin, etc. Now that I'm on the East Coast there is much more moisture in the air here. I've been using glycerin well past my usually cut-off month without any probs.